1. Field of the Invention
The present invention relates to a folding machine of a rotary press of the type that after superposed paper sheets have been cut out by means of a folding drum and a cutting drum, a folding blade is projected from the same folding drum to insert the cut paper sheets between a pair of folding rollers for folding them.
2. Description of the Prior Art press in the prior art with reference to FIGS. 13 and 14, reference numeral 1 designates superposed paper webs formed by superposing a plurality of traveling paper webs, numeral 2 designates a pair of nipping rollers, numeral 3 designates a cutting drum, numeral 4 designates a folding drum, numeral 5 designates a folding blade provided in the same folding drum 4, numerals 7a and 7b designate a pair of folding rollers, numeral 9 designates a runner, and numeral 10 designates a paper sheet discharging conveyor. The arrangement is such that superposed paper webs 1 consisting of a plurality of traveling paper webs superposed on one another are led through a gap between the pair of nipping rollers 2 to a gap space between the cutting drum 3 and the folding drum 4, where they are cut into cut paper sheets 6. Subsequently, the folding blade 5 provided in the folding drum 4 is projected to insert a central portion of the cut paper sheets 6 into a gap space between the pair of folding rollers 7a and 7b. The paper sheets 6 are thereby pinched by these folding rollers 7a and 7b to form twice-folded portions 6a and 6b and to discharge them downwards through the gap clearance between the folding rollers 7a and 7b. Further, the twice-folded paper sheets are made to fall on the paper sheet discharging conveyor 10 via the runner 9 to be sent to a subsequent step.
In the folding machine of a rotary press shown in FIGS. 13 and 14, for the purpose of regularly performing folding of the cut paper sheets 6, it is necessary to adjust gap clearances Sa and Sb between the pair of folding rollers 7a and 7b and the folding blade 5 depending upon a number of completed pages, and to that end a gap adjusting device as shown in FIG. 9 is provided. Reference numeral 08 in FIG. 9 designates a screw shaft having both left-hand and right-hand threads 08a and 08b, and to this screw shaft 08 is transmitted the rotation of a motor or a handle 013 in a driving device via a coupling 014. When the screw shaft 08 rotates, joint members 015 restrained from rotation, would slide in the directions of arrows A and B jointly with adjusting nuts 018 which have female screws and threadedly engage the screw shaft 08. Hence arms 022a and 022b are rotated about fulcrum points at the center of support shafts 023a and 023b via links 021 and pins 024a and 024b, and thereby a gap space S between the folding rollers 7a and 7b is adjusted. It is to be noted that a spring 26 biases the joint members 015 so that they may be always butted against shoulder portions of the adjusting nuts 018.
As described above, while the gap adjusting device for the folding rollers shown in FIG. 9 is a device making use of a single spring 026, as one example of known prior art devices making use of two springs, a folding mechanism for use in a rotary press disclosed in Laid-Open Japanese Patent Specification No. 51-115120 (1976) is shown in FIGS. 10, 11 and 12 of this application. In this folding mechanism for use in a rotary press, blocks 035 and 036 are swingably supported via cushion rubbers 043 and 044 from tip end portions of sup port arms 032 and 031, respectively, which in turn support folding rollers 7b and 7a, respectively, and can rotate about support shafts 034 and 033, respectively. In addition, stop members 037 and 038 fit around eccentric cams 045 and 046 mounted to a shaft 047. At an axial end portion of the shaft 047 is fixed a worm wheel 048, which is adapted to be rotated by a worm 049. Hence as a result of rotation of the worm 049, the eccentric cams 045 and 046 rotate, thus the support arms 031 and 032 are rotated via the stop members 037 and 038 and the blocks 035 and 036, and the gap space S between the folding rollers 7a and 7b can be adjusted. At this time, the stop members 037 and 038, the blocks 035 and 036 and springs 041 and 042, respectively, would move integrally.
However, in the gap adjusting device for the folding rollers in the prior art shown in FIG. 9, in the event that a deviated load has been applied to the device, the respective folding rollers would mutually affect each other via the springs such that the respective folding rollers would rotate and vibrate. Therefore, normally an arm on one side (the arm 022b in FIG. 9) is fixed. But if the gap space between the respective folding rollers is made smaller than the thickness of the paper sheets for the completed pages in order to insure the folding, since the gap space between the fixed side folding roller and the folding blade is small, breaking or damages may be produced in the paper sheets and thus just the opposite effect would be brought about. Therefore, it is practically impossible to reduce the gap space between the respective folding rollers up to a gap distance smaller than the paper sheet thickness of the completed pages, and a high precision setting of the gap space between the respective folding rollers is required.
On the other hand, in the heretofore known folding mechanism for use in a rotary press shown in FIGS. 10, 11 and 12, in the case where it is necessary to make the arms large, the mass of the arms also become large, hence a shock upon the operation is large. Countermeasures for enhancing the mechanical strength, preventing abrasion and lowering the noise level become necessary. In view of this necessity, in the folding mechanism for use in a rotary press shown in FIGS. 10, 11 and 12, special cushion rubbers 043 and 044 are mounted to the shafts 051 and 052 for connecting the support arms 032 and 031 with the stop members 037 and 038. However, since they are elastic bodies, they would plastically deform, and the preset gap space would change. In addition, since the adjustment of the gap space is performed by means of eccentric cams, a worm wheel and a worm for driving the eccentric cams, the cam shaft would rotationally vibrate as the result of an impact force. Hence, the worm wheel and the worm are liable to generate surface peel at their contact surfaces. Moreover, in the event that the machine is operated with the gap space preset to be small with respect to the number of completed pages in order to form a fold in a group of thickly superposed sheets, there were problems in that response characteristics of the folding rollers, which continuously and periodically pinch paper sheets, would be deteriorated, the pressing would become unreliable and the pressing force would become insufficient because the mass and inertia of the arms are large, as described above.
In addition, in the case where a number of completed pages is large (thick pages), a fold was barely formed at the boundary between the twice-folded portion 6a and the twice-folded portion 6b by merely adjusting the above-mentioned gap space between the pair of folding rollers 7a and 7b with the aid of the gap adjusting device for folding rollers in the prior art as shown in FIG. 9. Therefore, the folding machine was stopped and the folding blade 5 was adjusted in such manner that a distance Ak (See FIG. 6) between the tip end of the folding blade 5 and the straight line connecting the centers of the pair of folding rollers 7a and 7b may become larger than a corresponding distance An (See FIG. 7) in the case of a small number of completed pages (thin pages).
However, in a recent rotary press, the number of completed pages of paper sheets is increasing and the page number difference between thick pages and thin pages is expanding. Accordingly, even if the gap space between the folding rollers 7a and 7b is adjusted with the position of the tip end of the folding blade 5 held at the position corresponding to thin pages, the state shown in FIG. 8 occurs. Hence when superposed paper sheets 6 having thick pages are folded, a fold is not given to the paper sheet on the outside, and the tip end portion at the location to be folded would come out of the folding machine in a swelled condition. Consequently, when the folded paper sheets are stacked up in a subsequent processing apparatus, for instance, on a paper sheet discharging conveyor 10, they would fall down. If one intended to forcibly form a fold with the pressing force of the folding rollers 7a and 7b being increased by strengthening the resilient forces of the springs (for instance, the spring 026 in FIG. 9 or the springs 041 and 042 in FIGS. 10-12), merely the forces for pressing the side surface of the folded paper sheets are increased and a fold is not formed. On the contrary the paper sheets are damaged by the folding rollers 7a and 7b, resulting in faults in quality. In the case where superposed paper sheets 6 having thin pages are folded with the tip end portion of the folding blade 5 kept adjusted at the position corresponding to thick pages as shown in FIG. 7, even if the gap space between the folding rollers 7a and 7b is adjusted, the superposed paper sheets 6 cannot be forcibly inserted into the gap space between the folding rollers 7a and 7b, and this causes stopping of paper sheets. For the above reasons, it is necessary to adjust the position of the tip end of the folding blade 5 with respect to the folding rollers 7a and 7b according to the completed pages, but this adjustment requires skill. In addition, since the above-mentioned adjustment is carried out after stopping the folding machine, there is a problem in that the rate of operation of the rotary press is lowered.